1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to an all-in-one type light guide plate and a backlight apparatus employing the same.
2. Description of the Related Art
In general, backlight apparatuses serve to illuminate a flat display device such as a liquid crystal display device. The backlight apparatuses are mainly classified as direct light type backlight apparatuses or light guide type backlight apparatuses. The light guide type backlight apparatuses are classified as flat type backlight apparatuses or wedge type backlight apparatuses.
In the direct light type backlight apparatuses, a light source is located at the back of a light output surface, thus enabling a planar lighting. It is possible to increase brightness by arranging a plurality of light sources as compared with the light guide type backlight apparatuses. In addition, it is possible to widen an area to be illuminated. However, power consumption is also increased. In a case where the direct light type backlight apparatuses are thin, it is difficult to sufficiently diffuse light. Accordingly, a shape of a lamp is projected onto a display screen. Uniformity of brightness is considerably decreased.
The light guide type backlight apparatuses have a structure in which light is incident onto an edge of a light guide plate and output to a light output surface of a light guide plate perpendicular to the incident light. Since the light source is located at the edge or side surface of the light guide plate, the number of light sources is limited due to a length of the side surface of the light guide plate. However, it is easy to make the light guide type backlight apparatuses thin. A structure for uniformly distribute brightness over the entire light emitting surface is complex as compared with the direct light type backlight apparatuses.
The flat type backlight apparatuses are employed for monitors or a case where high brightness is required. In the flat type backlight apparatuses, light sources may be fixed to four edges of a light guide plate. In order to increase brightness by arranging a plurality of light sources, a thickness of side surfaces of the light guide plate has to be uniform.
The wedge type backlight apparatuses are employed for devices which does not use a plurality of light sources because power consumption is limited. In the wedge type backlight apparatuses, a surface of a side of a light guide plate onto which light is incident from a light source has a large width, and other surfaces of the light guide plate have a small width. Accordingly, it is possible to reduce weight of backlight apparatuses.
Light sources used for the light guide type backlight apparatuses are classified as linear or filamentary light sources or point light sources. The linear or filamentary light sources are cold cathode fluorescent lamps (CCFLs) with a structure in which electrodes of both ends are located in a tube. The point light sources are light emitting diodes (LEDs). The CCFLs can emit intensive white light. It is possible to obtain high brightness and uniformity and to design backlight apparatuses so as to illuminate a large area. The CCFLs operate by using high frequency alternating current (AC) signals and have a narrow range of operating temperature. The LEDs have lower performance in brightness and uniformity than the CCFLs. However, the LEDs operate by using direct current (DC) signals. The LEDs have a long lifetime and a wide range of operating temperature. In addition, it is possible to make backlight apparatuses thin.